EJB Bad Practices: Use of Synchronization Primitives

The EJB specification explicitly prohibits the use of thread synchronization mechanisms like synchronized blocks or locks within enterprise beans. This rule exists because the container, not the developer, must manage concurrency and threading to ensure predictable behavior across different deployment environments. Violating this guideline creates portability risks. Some EJB containers run all bean instances in a single Java Virtual Machine (JVM), while others distribute them across multiple JVMs. Relying on synchronization primitives assumes a single JVM, which can lead to race conditions, deadlocks, or inconsistent behavior when the application is deployed to a compliant, distributed container.